Marine vessels, fishnets, and other underwater structures are susceptible to adhesion of organisms such as barnacles, mussels, and algae. The adhesion of such organisms will inhibit efficient navigation of the marine vessels or the like, and lead a problem such as a waste of fuel. In fishnets or the like, the problems arise such that clogging occurs and useful life decreases. Conventionally, for preventing the adhesion of organisms to such underwater structures, an antifouling coating is applied on the surface of the underwater structures.
On the other hand, when a coating (coating film) is formed in the site where friction occurs with respect to a liquid, as in marine vessels or the like, it is desired to reduce the friction resistance between the vessel and liquid by a coating film, from the viewpoints of reducing fuel consumption in navigation of marine vessels, saving energy and the like.
As a coating composition capable of reducing such friction resistance, coating compositions containing a binder resin in which metal such as organotin, copper or zinc is introduced in the form of a salt into an acrylic resin side chain (also called a self-polishing type coating composition or hydrolyzable coating composition) are conventionally known (for example, Japanese Patent Laying-Open No. 62-57464 (Patent document 1)). A coating film formed from such a conventional self-polishing type coating composition (hydrolyzable coating composition) is gradually hydrolyzed by water such as sea water during navigation of the marine vessel, and as a result, roughness of the surface irregularities generated in formation of the coating film is reduced, and an effect of reducing friction resistance is exhibited. However, it cannot be said that the low frictional performance of the conventional self-polishing type coating composition is satisfactory, and a coating composition exhibiting better low friction resistance has been desired. For example, WO 05/116155 pamphlet (Patent document 2), Japanese Patent Laying-Open No. 2006-328244 (Patent document 3) and Japanese Patent Laying-Open No. 2007-169628 (Patent document 4) disclose coating compositions containing specific organic polymer particles or composite particles having a particle diameter of 0.05 to 100 μm as a coating composition for the purpose of further reducing friction resistance. However, also in these coating compositions, there is a room for improvement in low frictional performance.